When pelletizing or sintering ore, the bulk material to be treated (for example iron ore or zinc ore) is loaded onto a pallet car where a plurality of cars forms an endless chain, also referred to as traveling grate. The pallet cars are filled with the bulk material and pass through various treatment stations, in which a thermal treatment of the material, such as drying, firing and cooling, is effected.
The pallet cars which are moved along an endless path into the sintering furnace experience high radiant heat as the material to be sintered is treated. The pallet cars experience substantial differential heating and cooling, in repetitive cycles, and as a consequence, their components tend to expand and contract leading to warping and cracking, as well as loosening of components relative to each other.
Pallet cars include a loading bay for receiving bulk material to be treated. The loading bay is subjected to harsh conditions. The floor of the loading bay, comprising a plurality of grate bars, supports the weight of the bulk material, Differential heating and cooling of grate bars can lead to warping, cracking and loosening of connections. As is expected, grate bars are subjected to very high temperatures and existing pallet cars are built with floors with air slots to permit venting of hot gases. An exemplary prior art grate bar is shown in FIG. 1. Prior art Grate bar comprises an elongate body 1 including a top surface for supporting bulk material to be treated, a pair of opposed arms 2, and a pair of opposed feet 3. A pair of peripheral spacers 4 extends laterally away from the body 1 in opposing directions by a spacer width.
A pair of central spacers 5 extend laterally, a certain distance, away from the body 1 in opposing directions by a spacer width. Central spacers 5 are located intermediate the opposed arms 2 of the grate bar.
The top wall of peripheral spacers 4 and central spacers 5 are flush with the top surface of the body 1 and therefore, the material to be treated contacts the top wall of spacers 4, 5.
Existing grate bar has length A and gap length L which is the combined distance (l+l) between each peripheral spacer on each end of the grate bar and the central spacer. A plurality of grate bars are placed in adjacent and abutting relationship with each other such that the peripheral spacers 4 and the central spacer 5 of one grate bar abuts against the peripheral spacers 4 and the central spacer 5, respectively, of an adjacently placed grate bar. Air slots 6 are formed in the space defined by paired peripheral spacers 4 and the central spacer 5 of adjacent grate bars. Air slots 6 allow for movement of gases between the adjacent grate bars. The width of air slots 6 is determined by the sum of the spacer widths of each adjacent grate bar. It will be appreciated that existing grate bars are bulky and thick and have poor venting characteristics and their use can result in warping, cracking and loosening of connections of the pallet car.
Therefore, there is a need to provide a grate bar for a sintering pallet car that overcomes the drawbacks of existing grate bars.